1. Networks

2. What is a computer network?
A network is two or more computers that are linked together so that they are able to share resources.
Users can protect their work on a network by having a strong password, and changing it frequently.

3. Shared resources include
Hardware – printers, scanners, storage, etc.
Software – need only be installed on one computer.
Data (e.g. database files).
An Internet connection.

4. LANs and WANs Local area networks: Wide area networks:
Confined to a small area.
Usually located in a single building.
Use cable, wireless, infrared and microwave links that are usually owned by the organization.
Cheap to build.
Cheap to run.
Wide area networks:
Cover a wide geographical area (i.e., between cities, countries and even continents).
In lots of different buildings and cities, countries, etc.
Use more expensive telecommunication links that are supplied by telecom companies.
Expensive to build.
Expensive to run.

5. An ICT network consists of
Hardware/communication devices
Network software
Data transfer media

6. Network Topologies Bus
PCs connected to the next in a row with a central backbone
If a PC or link fails or breaks the whole system fails
The more PCs the poorer the performance
Difficult to locate faults
Easy to add additional PCs

7. Ring Fast Better, faster performance than a bus topology BUT
If one cable breaks then all computers will not work, as data only travels in one direction.

8. All PCs and peripheral devices connected to switch/router/hub.
Star Network
If one cable breaks or one device fails the rest continue to work
Easy to maintain and add PCs, no loss in performance
Large amount of cabling needed
Expensive to buy needed hardware (hubs and switches etc)

9. Company-School-Hospital Intranet
Robert-Hole
Gurney-Dixon
An Intranet is a private network, usually several buildings linked together with fibre-optic cable to the main server building. Think of Learners Pool.
Tech
Main Block
Firewall
IPS servers
Nichols
Internet

10. Company-School-Hospital Extranet
This is when employees or users of a private Intranet can gain access to this network away from their place of work, or school.
An example is you using Ranger Outpost to gain access to the private Priestlands School Intranet.

11. Communication devices
A hub:
is used to join computers in a network
allows the connection of cables
allows the sharing of files and Internet access
A hub can cost about £200. Home computers may still have hubs but in schools they use switches.
In a hub network if you had 7 computers and 1 printer attached to the hub and 1 computer sent a message to say they wanted to print all the computers would get this message. This can cause a collision, this is why over the last 5 years hubs are not being used as much and are being replaced by switches.

12. Communication devices
A switch:
is similar to a hub but more intelligent
It can look at a packet of data to decide where it should go. For example;
A hub network has 7 computers and 1 printer attached. When 1 computer sends a message to the printer to print, the request goes to everything on that hub, trying to find the printer. This can cause a collision of data, slowing the network down.
A switch allows the computer wanting to print to go straight to the printer and not waste time trying to find it. Hubs are therefore being replaced by switches.
reduces the number of packets of data on a network, which speeds it up
One switch at school costs about £1000 because it can make decisions. It has 2 fans to stop over heating. Management system can be looked at remotely so if any errors ICT technicians can see the problem from their own office. Easy to control.
Takes time to set up, cost a lot for a LAN.

13. Communication devices
A router:
IS VERY POWERFUL and can be wired or wireless
is used to join several networks together
is often used to connect several computers in the home to the Internet

14. Network software Network software consists of:
Network operating systems – specialist operating systems designed specifically for networks.
Network management software – used to help a network manager run a network by keeping track of software, keeping software up-to-date, installing software security patches, helping to manage the help-desk, etc.

15. Data transfer media The medium/method by which the data is
transferred in a
network can be:
metal wire
fibre optic cable
wireless.

16. Gateways Joins together two networks that use different base protocols
Links different types of networks
Links LAN to WAN
Allows a LAN to connect to the internet

17. Bridge Joins together two networks that use the same bas e protocols.
Links similar types of networks.
Links LAN to LAN.

18. Tasks:
What is a network?
Why do we have them?
What can they share?
What 3 types of topologies are there? Explain the differences and advantages of each.
What is a LAN? Give an example.
What is a WAN? Give an example.
What is an INTRANET? Give an example.
What is an EXTRANET? Give an example.
What is a hub?
What is a router?
What is a switch, and what does it do?
What is a Bridge?
What is a Gateway?
Give 2 ways of protecting data on a network.